Disabling RTL2832 AGC

Steve Markgraf Steve.Markgraf at student.hs-rm.de
Sun Jul 8 10:01:03 UTC 2012


On 07.07.2012 20:27, Leif Asbrink wrote:
> As far as I can see there is no difference when I set 0x05 or
> 0xd5. The bits are no longer unknown - the posting from
> Steve Markgraf tells us that they mean nothing for a e4000
> in "serial interface gain control mode" so the appropriate value
> should be 0x05.

No, I was not referring to the bits in register 0x19, but to the
piece of code that Francesco posted earlier (which writes to
registers in page 1).

> Steve Markgraf wrote 2012-06-22:
>> The remaining AGC that's active is not in the E4K, but it's the 
>> Digital
>> AGC (DAGC) of the RTL2832. Unfortunately we don't know how to 
>> disable
>> it, since the way it's supposed to be disabled does not work.

> That is somehow in contrast to Steves latest posting....

It is? Notice the date of the post. We did not know how to disable
it until you figured out, I played around with register 0x19
earlier though, but managed to overlook the effect of bit 5.
The "way it's supposed to work" I was referring to is clearing bit
0 of register 0x11 in page 1, which has no effect at all (en_dagc).

I've now pushed a change to librtlsdr that disables the AGC by
default, and added the function rtlsdr_set_agc_mode() that can
be used to re-enable it again.


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